URTICACE.E. (NETTLE FAMILY.) 435 



many as and opposite the sepals. Filaments inflexed in the bud, ex- 

 panding elastically: anthers 2-celled, introrse. Calyx of the fertile 

 flower 2-4-sepalous. Ovary sessile, free, 1-celled, with a single erect 

 orthotropous ovule. Stigma simple or tufted. Acheriium commonly 

 enclosed in the dry persistent calyx. Embryo straight, in the axis of 

 fleshy albumen. 



Synopsis. 



* Plants armed with stinging hairs. 



1. URTICA. Stamens 4. Stigma tufted. Achenium straight. 



2. LAPORTEA. Stamens 5. Stigma subulate. Achenium oblique. 



* * Plants destitute of stinging hairs. 

 i- Flowers in cymose clusters. 



3. PILEA. Clusters naked. Calyx lobes unequal. Leaves opposite. 



4. PARIETARIA. Clusters involucrate. Calyx lobes equal. Leaves alternate. 



i- <- Flowers in spiked clusters. 



5. BCEHMERIA. Stigmas subulate, leaves opposite or alternate. 



1. URTICA, Tourn. NETTLE. 



Flowers monoecious or dioecious. Calyx of the sterile flower 4-parted. 

 Stamens 4, inserted around the abortive ovary. Calyx of the fertile flower 

 4-sepalous, unequal ; the inner sepals dilated in fruit, and enclosing the ache- 

 uium. Stigma sessile, tufted Achenium straight, ovate, smooth, compressed. 

 Herbs, with stinging hairs, opposite leaves, and greenish flowers, in pani- 

 cled spikes or close clusters. 



* Flowers in paniclcd or simple spikes. 



1. II. gracillS, Ait. Stem tall, 4-angled, smoothish, slender; leaves 

 long-petioled, ovate-lanceolate, coarsely serrate, acute, rounded at the base, 

 3-5-nerved, smoothish, the petioles bristly ; spikes very slender, loosely pani- 

 cled. Low ground in the upper districts. July -August. 11 Stem 3- 

 4 high, mostly simple. Leaves thin, 4' -6' long. 



2. TJ. dioica, L. Hispid throughout ; stem 4-angled, pubescent above, 

 branching; leaves rather short-petioled, ovate, cordate, acuminate, coarsely 

 serrate, pubescent beneath ; spikes much branched ; flowers often dioe- 

 cious. Waste places, Carolina (Pursh). Introduced. June -August. ^ 

 Stem 2 -3 high. Leaves 3' -4' long, thicker than in No. 1, aud flowers 

 larger. 



* * Flowers in simple clusters shorter than the petioles. 



3. U. urens, L. Stem 4-angled, hairy ; leaves ovate, coarsely serrate, 

 5-nerved, hairy ; clusters by pairs in each axil, loose, peduncled. Waste 

 ground. Introduced. Dec. -Feb. (T) Stem 1 high. 



4. IT. Cham.8edryoid.es, Pursh. Stem smooth ; leaves small, nearly 

 sessile, ovate, coarsely serrate., hairy beneath, hairy and bristly above ; clus- 

 ters nearly sessile, globose, dense; calyx hairy. Georgia (Elliott), and west- 

 ward. Feb. - March. Stem 4' - 12' high. 



